1. Field of Invention
Exemplary aspects of the present invention relate to an image forming apparatus that makes use of an electrophotographic process, such as a copier, a printer, a facsimile, a plotter, or a multi-function machine having a combination of these functions, and more particularly to an image forming apparatus having a device for carrying out position determination of a rotating body.
2. Description of Related Art
Related art image forming apparatuses such as copiers, printers, facsimiles or multi-function machines having a combination of these functions use an electrophotographic process. A related-art color image forming apparatus is one of the above-mentioned image forming apparatuses. The related-art color image forming apparatus includes a plurality of image carriers for different basic colors, and particularly needs accurate positioning of each of the plurality of image carriers. Each image carrier is typically formed as a photoreceptor drum and may be assembled together with associated components into a so-called process cartridge to provide a convenient replacement in a cartridge form. That is, each of a plurality of process cartridges for different basic colors is detachably installed in a related-art color image forming apparatus. Based on such a structure, preventing a displacement of images has been a critical issue. Therefore, in an effort to address such a problem, various types of methods have been proposed and practiced according to, for example, Japanese Patent Laid-Open Application Publications, No. JP04-229889, No. JP2004-177443, No. JP10-7260, No. JP2004-233902, No. JP2001-242671, and No. JP2001-222207.